Process of manufacturing sugar



Patented May 23, 1950 PROCESS OF MANUFACTURING SUGAR Herman Schreiber, Lansing, Mich.

No Drawing. Application April 1, 1946,

'7 Claims. 7 1

The present invention relates to an improved process of manufacturing or purifying sugar, and

is more particularly concerned with the treat-,

ment of sugar cane juice whereby the yield and quality of the ultimate sugar product is improved.

Generally speaking, it is the present practice to lime raw cane juice to the desired alkalinity, heat to boiling, and then allow the juice to settle. The clarified middle portion of the settled juice is evaporated to a syrup and then this syrup is boiled to recover the crystallized sugar. In order to obtain economical crystallization of the sugar, massecuites are boiled from various mixtures of this syrup and materials of lower purity, such as molasses or semilia.

As is known to those skilled in the art, there are various programs for carrying on the boiling process to recover a maximum quantity of sugar in crystalline form and to permit a minimum amount to go to final molasses. It may be a 2 or 3 massecuite program, which means that sugar is recovered in two or three operations from massecuites of successively lower purity. When the initial syrup is high enough in purity, three massecuites are boiled, and the molasses from the third massecuite is discarded. In such a system it is customary to boil the various massecuites about as follows:

Massecuite #1 may consist of semilia (the sugar from a third massecuite mixed with syrup) plus five parts syrup plus one to two parts molasses from a previous first massecuite. Thus a #1 massecuite will contain a foot or starter of grain from a third massecuite onto which is boiled fresh syrup and then molasses from a preceding massecuite #1. Massecuite #1, in other words, is commonly a mixture of the syrup from cane, lower grade material from a third massecuite, and molasses from a preceding like #1 massecuite.

Massecuite #2 is sometimes boiled from syrup,

..on..virgin grain obtained from syrup, and 3 to 4 parts molasses from previous massecuite #1.

Massecuite #3 is sometimes boiled on virgin grain with about half as much syrup as used in massecuite #2 and about twice as much molasses 1 Serial No. 658,876

actions occur which result in a continuous decrease in the pH of the successive molasses obtained, so that molasses from last products are frequently quite low in pH. The drop in pH from syrup to first molasses is sometimes 1.0 pH.

Because of the small purification efiected by conventional liming, syrup can be boiled to a massecuite directly only by long, slow boiling with unsatisfactory yields and manufacturing conditions. The same holds true in attempting to boil molasses directly to a second massecuite.

It is the purpose and one of the prime objects of the present invention to provide a process wherein recirculation and reboiling of molasses is done away with and whereby the continuous decrease in the pH of the successive molasses is at least held to a minimum.

It is a further object to provide a process wherein improved yields are obtained by boiling syrup directly to a first massecuite and then boiling molasses from the first massecuite directly to a second massecuite with no low-purity materials being introduced into the system.

In my prior Patent No. 1,724,376, issued August 13, 1929 (the disclosure of which is incorporated herein by reference), I have described and claimed a, process for purifying raw sugar cane juices involving a. moderate heating of the raw juices at a point substantially below the boiling point of the juices, usually not higher than 0., whereby non-sugars are thrown out of solution, and then lime added to the proper pH followed by heating of the limed juices until a clear solution results. The foregoing moderate heat treatment may be carried out in the presence of added precipitants or proteolytic enzymes. The quantity of lime added may or may not be sufiicient to give the juices an alkaline reaction but is suflicient to adjust the hydrogen ion concentration to that desired by the operator as seems best with reference to the raw material undergoing treatment. The hydrogen ion concentration can vary from 6.5 to 8 or more and ultimately depends upon the character of the juices treated and the preferences of the operator.

The limed juices are then heated to a temperature equal to or higher than the temperature at which the raw juices were previously maintained, as described above, and are kept at this temperature until a clear brilliant solution results. Usually I heat in the second step to a temperature of 70 to C. While I can boil the sugar solution in this heating step, I find it 3 usually better not to heat the sugar iuice high enough to cause ebullltion. The length of time during which I maintain the limed solution hot is advantageously from 40 to 90 minutes although the exact length of time depends upon the character of the raw sugar juice being treated. The completion of this heating step is readily determined by the experienced sugar operator, usually by observing the appearance of the juice.

After this second heating operation. I then separate the clear brilliant juices from any separated non-sugars. In a sense, the foregoing process of my prior patent may be described as a double purification of the sugar cane juice, I. e. (1) preliminary mild heat treatment to throw out non-sugars, followed by (2) liming. This double purification has been found to yield a juice having between 1 and 2% higher purity than when lime alone is used. However,

when this purified juice is subjected to the practice current in cane sugar mills in the boiling process, as hereinbefore generally defined, no considerable benefit will be obtained in the yield of sugar. This is no doubt due to the fact that while the initial juice is of higher purity, the continuous recirculation and reboiling of molasses introduces non-sugars and other impurities.

It has now been found, in accordance with the present invention, that by employing the socalled double purification of the sugar cane juice, as set forth in my aforementioned patent, it is possible to evaporate the purified juice to syrup and then crystallize the sugar therefrom by boiling massecuites from syrup alone and first molasses alone without the addition of molasses or other materials from previous crystallizations. Thus the recirculation and reboiling of molasses as in the prior art is obviated.

According to the process or the present invention, the raw cane juice is first maintained at a temperature below the boiling point, with or without addition of special reagents, to obtain a preliminary separation of non-sugars. The partly clarified juice from this separation is treated with lime (CaO) in the usual manner, dependent upon the lime requirement of the juice at a given locality. The purified juice from this step is then evaporated to syrup. The syrup is boiled, without the addition of recirculated molasses, directly to a first massecuite. The crystallized sugar is separated from the massecuite by centrifuge. The molasses (mother liquor) from the first massecuite is then boiled directly to a second massecuite. The molasses from the second massecuite is boiled to a third massecuite, either directly or on a footing of virgin grain or semilia. This third massecuite issent to crystallizers, held, and then purged. The third molasses may be discarded. The third sugar may either be washed and sold as obtained, or if thought desirable mixed with fresh syrup or first molasses and returned to be used as footing for an appropriate massecuite. There is much less third sugar and it is of much higher quality, so this is no problem.

It is understood that where the syrup is of such low purity that only two boilings are possible, the same system is maintained. Where the syrup obtained is of such high purity that the desired drop in purity to final molasses is not obtained by the three boilings or three massecuite' systems, then four massecuites are boiled. As a result of not recirculating or adding molasses to a subsequent massecuite of higher purity than that of the molasses, the pH of the first and second molasses does not drop appreciably. The sugar crystallizes more completely and is of much higher quality. As a further consequence there is less destruction and loss of sugar appearing as non-sugar in the final molasses. Thus the quantity of final molasses obtained is decreased as much as 60%, resulting in an increased yield of higher quality sugar. The amount of increase in sugar yield depends upon the loss of sugar ordinarily occurring in a, given locality-and ranges from about pounds of sugar per ton of cane upwards.

In the process of this invention it is possible to boil syrup alone to a massecuite #1, molasses from massecuite #1 alone to a massecuite #2, and obtain much less molasses #2 than in the former practice and much less molasses #3 from a subsequent #3 massecuite. The decrease in the amount of molasses #2 and #3 is as much as 60% and, therefore, an increase in sugar is produced equivalent to this difference, which is ordinarily lost in #3 molasses.

To illustrate more clearly the advantages of the present process over those of the prior art, attention is directed to the following table comparing the lowering of the pH in the successive boiling steps:

From conventional The present lime puriiiinvention cation Clarified Juice 7. 5 7. 2-7. 8 S 7. 2-7. 4 7. 2 6. 2-6. 7 7. 0 6. 2-6. 5. 6.8-7. 0 96 Sugar 6. 6-6. 8 1 7. 0-7. 4

l pol. 97-98.

Furthermore, the final molasses resulting from the purification process in which lime only is used in the juice clarification, and in which the massecuites are boiled from mixtures containing molasses and syrup, had three times as much organic non-sugars (10%) as final molasses from the process of the present invention (ti /3%) It has been found, further in accordance with the invention, that if the juices purified in the manner outlined in my prior patent are employed in a straight boiling system wherein only the syrup coming from the evaporators is boiled to a first massecuite and the molasses purged from this massecuite is alone boiled to a second massecuite, with no addition or recirculation of extraneous materials, there is produced a sugar of better quality and one which has a higher polarization. Even a third sugar of 9''! polarization may be produced. The pH of the successive first and second molasses will not drop appreciably but will remain at a point near neutrality. Thus destruction of sugar to non-sugar organic substances is decreased.

Also, the amount of final molasses produced may be 60% less than by present practices. This means that a very decided increase in quantity of sugar is produced. This increase will vary with the locality as it results from a saving effected by recovery of sugar usually lost to molasses.

What is claimed is:

l, The process of manufacturing sugar which comprises subjecting raw sugar cane juice to a double purification which includes maintaining the raw juice at a moderately elevated temperature but substantially below the boiling point of the juice until no further separation of nonsugars occurs, separating the juice from the nonsugars thrown out of solution or suspension, adding sufiicient lime to the juice so that, upon further heating, a clear liquid results, and then evaporating the thus purified juice to a syrup, boiling the syrup directly to a massecuite without the introduction of extraneous materials, and recovering sugar from the massecuite.

2. The process of manufacturing sugar which comprises subjecting raw sugar cane juice to a double purification which includes maintaining the raw juice containing an added precipitant at a moderately elevated temperature but substantially below the boiling point of the juice until no further separation of non-sugars occurs, separating the juices from the non-sugars thrown out of solution or suspension, adding sufiiclent lime to the juice so that, upon further heating, a clear liquid results, and then evaporating the thus purified juice to a syrup, boiling the syrup directly to a massecuite without the introduction of extraneous materials, and recovering sugar from the massecuite.

3. The process of manufacturing sugar which comprises subjecting raw sugar cane juice to a double purification which includes maintaining the raw juice at a moderately elevated temperature but substantially below the boiling point of the juice until no further separation of nonsugars occurs, separating the juice from the nonsugars thrown out of solution or suspension, adding sufficient lime to the juice so that, upon further heating, a clear liquid results, and then evaporating the thus purified juice to a syrup, boiling the syrup directly to first massecuite without the introduction of extraneous materials,

a clear liquid results, and then evaporating the .thus purified juice to a syrup, boiling'the syrup directly to a first massecuite without the introduction of extraneous materials, recovering sugar from the massecuite, boiling the molasses from the first massecuite directly to a second massecuite, and recovering sugar from the second massecuite.

5. The process of manufacturing sugar which comprises subjecting raw sugar cane juice to a double purification which includes maintaining the raw juice at a moderately elevated temperature but substantially below the boiling point of the juice until no further separation of nonsugars occurs, separating the juice from the nonsugars thrown out of solution or suspension, adding suflicient lime to the juice so that, upon further heating, a clear liquid results, and then evaporating the thus purified juice to a syrup, boiling the syrup directly to a first massecuite, without the introduction of extraneous materials, recovering sugar from the massecuite, boiling the molasses from the first massecuite directly to a second massecuite, recovering sugar from the second massecuite, boiling molasses from the second massecuite directly to a third massecuite, and recovering sugar from the third massecuite.

6. The process of manufacturing sugar which comprises subjecting raw sugar cane juice to a double purification which includes maintaining the raw juice at a moderately elevated temperature but substantially below the boiling point of the juice until no further separation of nonsugars occurs, separating the juice from the nonsugars thrown out of solution or suspension, adding suificient lime to the juice so that, upon further heating, a clear liquid results, and then evaporating the thus purified juice to a syrup, boiling the syrup. directly to a first massecuite without the introduction of extraneous materials, recovering sugar from the massecuite, boiling the molasses from the first massecuite directly to a, second massecuite, recovering sugar from the second massecuite, boiling molasses from the second massecuite directly to a third massecuite on a footing of semilia, and recovering sugar from the third massecuite.

7. The process of manufacturing sugar which comprises subjecting raw sugar cane juice to a double purification which includes maintaining the raw juice at a moderately elevated temperature but substantially below the boiling point of the juice until no further separation of nonsugars occurs, separating the juice from the nonsugars thrown out of solution or suspension, adding suificient lime to the juice so that, upon further heating, a, clear liquid results, and then evaporating the thus purified juice to a syrup, boiling the syrup directly to a first massecuite without the introduction of extraneous materials,

- recovering sugar from the massecuite, boiling the REFERENCES CITED The following references are of record file of this patent:

UNITED STATES PA'II'ENTS Name Date in the Number OTHER REFERENCES Deerr: Cane Sugar," London, 1921, pages 391 and 392.

Spencer: Cane Sugar Handbookj'jth ed., New York, 1945.

Schreiber A118. 13, 1929 

1. THE PROCESS OF MANUFACTURING SUGAR WHICH COMPRISES SUBJECTING RAW SUGAR CANE JUICE TO A DOUBLE PURIFICATION WHICH INCLUDES MAINTAINING THE RAW JUICE AT A MODERATELY ELEVATED TEMPERATURE BUT SUBSTANTIALLY BELOW THE BOILING POINT OF THE JUICE UNTIL NO FURTHER SEPARATION OF NONSUGARS OCCURS, SEPARATING THE JUICE FROM THE NONSUGARS THROWN OUT OF SOLUTION OR SUSPENSION, ADDING SUFFICIENT LIME TO THE JUICE SO THAT, UPON FURTHER HEATING, A CLEAR LIQUID RESULTS, AND THEN EVAPORATING THE THUS PURIFIED JUICE TO A SYRUP, BOILING THE SYRUP DIRECTLY TO A MASSECUITE WITHOUT THE INTRODUCTION OF EXTRANEOUS MATERIALS, AND RECOVERING SUGAR FROM THE MASSECUTE. 